Kites have been in existence for hundreds of years. They are generally made with wood, solid or tubular fiberglass, carbon rods, light weight plastic, and/or fabric. The kite is a tethered aerodyne and is in a stalled state against the wind. The disadvantage of a kite is that it needs line and wind to fly. Over the years, there have been a number of efforts directed towards the improvement of a power assisted flying device. These efforts have focused on improving the directional controls of radio controlled kite-like objects and airplane models.
In the mid 1990's Dan Kreigh of California developed a radio controlled kite-like flying object. The shape was formed by one fiberglass rod in a simple pattern of a semi-circle. Dan Kreigh's version of the radio controlled kite used rudder and elevators for control. In the late 1990's, Michael Lin of Singapore expanded on Dan Kreigh's approach by making the shapes more elaborate. However, Michael Lin's versions also depended on the use of rudder and elevators for control. All were controlled by moving control surfaces.
Moving control surfaces have been used on aircraft since the dawn of flight; however, they include many disadvantages for controlling kites. By nature, kites are often larger and slower moving than traditional remote controlled aircraft. While flying objects have great advantages for ease of remote controlled flight, slow moving flying objects need to have large lightweight wing areas and proportionally large moving surfaces to control flight. This is because when there is slow or no air rushing across a control surface, the control surface fails to move the object in the intended direction. Since kites by nature are slow moving, to steer them by moving control surfaces require very large moving surfaces, which in turn are difficult for most standard servos to move. Further, by nature, kites are much lighter per size than traditional aircraft and are able to sometimes “stop” and “float” on the wind. Moving control surfaces are completely ineffective at controlling an object that simply “stops” in the air.
In addition, moving control surfaces require hinges attached to ridged structures such as a fuselage or an airframe. Kites rarely have ridged members strong enough to attach the necessary hinges and control surfaces in the correct areas for effective control of the kite. Since moving control surfaces for kite-like flying objects have to be large, this condition results in more performance robbing weight and less room on the kite for lifting surfaces which are so important for an effective flying kite.
In 2006, Peter Loehnert of Solingen, Germany started to develop kite-like flying objects using a new vector thrust concept. Directional control was achieved by the use of a brushless electric motor, propeller and two servos. One servo provided the up-down motion control while the other servo provided the left-right motion control. The brushless electric motor and propeller were directly connected to the moving axle of the left-right servo and thus when the axle of the servo turned clockwise or counterclockwise, the motor and spinning propeller also shifted left and/or right thereby directing thrust and steering the kite left or right. The left-right servo, with the connected motor assembly, was then connected to the moving axle of the up-down servo. Thus, when the axle of the up-down servo turned clockwise or counterclockwise, the left-right servo, motor and spinning propeller moved up and down thus directing thrust to control the pitch of the kite. Pitch, yaw, roll and forward speed were achieved by the combination of up-down and left-right thrust positioning along with proportional speed control of the motor. Since the thrust on the propulsion unit can be totally directed by both magnitude and direction, the propulsion assembly is typically called a vector thrust control unit. In this system, no moving control surfaces are used or needed.
Although the Loehnert system worked well, there are several disadvantages to this system for motorizing and controlling kites. First, commercially available servos to this date are not designed to accommodate the stresses developed by direct linkage to the motor and other servos. Thus many servos were over-stressed and failed frequently, rendering the power unit useless. In addition, of the few servos available that could marginally withstand the stress, these servos were very high in price and difficult for many consumers to afford. Furthermore, all of the components—motor and servos—were glued together in one integral unit, making replacement of individual parts impossible.
U.S. Pat. No. 4,204,656 (Seward) discloses a freeflying miniblimp comprising a frame, a balloon containing lighter-than-air gas and a control system for said miniblimp, said control system consisting of a single drive motor, a propeller attached to said drive motor and rotated by said drive motor, a bracket to which is mounted said drive motor, an ascent/descent motor, first means for attaching said ascent/descent motor to said bracket to tilt said drive motor upward or downward, a left/right motor, second means for attaching said left/right motor to turn said drive motor left or right, a single fixed vertical stabilizer secured to said miniblimp and having an absence of moving parts, an energy source and control means for said motors functionally connected to said motors.
U.S. Pat. No. 7,109,598 (Roberts et al.) discloses one or more tethered platforms, each having three or more mill rotors, that are operated at altitudes in relatively high winds to generate electricity. These windmill kites use one or more electro-mechanical tethers on each platform. Their position, attitude and orientation are monitored by one or more GPS receivers and/or gyros and controlled through differential thrusts and torque-reactions produced by the mill rotors. The kites can be electrically powered from a ground supply during relatively calm periods, or landed if desired. During windy periods the kites may be used to generate electricity by tilting the rotors at an angle, or incidence to the on-coming wind. In this generate mode the mill rotors simultaneously develop thrust while generating electricity. See also U.S. Pat. No. 7,183,663.
U.S. Pat. No. 7,048,232 (Plottner) discloses a kite that is flown by means of two control lines and which has two counter rotating 50 inch rotors and which can be flown in winds of 9 miles per hour and greater. This rotor kite can take off, fly in the air at various heights and then be landed by the operator on its rear legs with no harm to the spinning rotors. Manipulation of the rotor kite in the air is possible at all times as the two major merits of this disclosure are its fly ability and its control ability.
U.S. Pat. No. 6,793,172 (Liotta) discloses an aircraft which is designed for remote controlled slow flight, indoor or in a small outdoor yard or field. The aerial lifting body is defined by a series of lightweight planar or thin airfoil surfaces (A1, A2, A3, A4) arranged in a radially symmetrical configuration. Suspended within the cavity (O) formed by the thin airfoil surfaces (A1, A2, A3, A4) is a thrust generating propeller system (C) that is angled upwardly and that can be regulated remotely so as to change the angle of the thrust vector within the cavity (O) for steering. Lifting, stability, turning, and general control of the direction of motion in flight is accomplished without any formal wings, rudder, tail, or control surfaces.
U.S. Pat. No. 6,257,525 (Matlin et al.) discloses a remotely controlled aircraft having a center member and a steering assembly. The steering assembly comprises a carriage, a remote control motor, a center member and a connecting arm. The carriage pivotably is attached to the center member. The remote control motor has a control arm and is disposed within the carriage. The center member arm has a first end and a second end. The first end of the center member arm is fixedly attached to the center member. The center member and the center member arm is arranged in a non-parallel manner. The connecting arm has a first end and a second end. The first end of the connecting arm is pivotably attached to the second end of the center member arm. The second end of the connecting arm is pivotably attached to the control arm of the remote control motor.
U.S. Pat. No. 5,034,759 (Watson) discloses an aerial still camera including: a video camera; a device for elevating the video camera relative ground level; structure for suspending the video camera from the elevating device; first self-leveling structure for leveling the video camera in a first direction; second self-leveling structure for leveling the video camera in a second direction; first drive structure for rotating the video camera to control the image scanned by the video camera along a first axis; second drive structure for rotating the video camera to control the image scanned by the video camera along a second axis; a tether attached at one end to the elevating device for holding the elevating device and the video camera in the elevated position, the tether including electrical conductors; and an electrical control device attached at another end of the tether for controlling the first and second drive structure so as to control the image scanned by the video camera, the control structure further including a video display so to display the image scanned by the video camera.